y= (1-x) e^x
Экстремума

y = (1-x)*eˣf'(x) = (1-x)'eˣ + (eˣ)'*(1-x) = -eˣ + eˣ(1-x) = eˣ(-1 + 1 - x) = eˣ*(-x)f'(x) = 0eˣ = 0    или    -x = 0x = ∅               x = 0